Forecasters reduce hurricane season predictions, slightly

by Artemis on August 6, 2013

Two of the forecasters we follow for their updates on the Atlantic tropical storm and hurricane season have reduced their predictions for the number of storms that will intensify to hurricane or severe hurricane status. Both of the forecasters continue to predict an above average 2013 Atlantic Hurricane Season.

We’re already two months into the six month Atlantic and Caribbean tropical cyclone season and have witnessed four named storms to date. None of the four tropical storms have made it to hurricane status and neither have they caused any significant impact to the insurance or reinsurance industry.

As the season progresses the forecasters watch both the current run-rate of tropical storm formation and the changing climatic, atmospheric and oceanic conditions to enhance their predictions for the seasons activity. Two of the forecasters we include on our 2013 Atlantic Hurricane Season page have provided recent updates, with both reducing their count for hurricanes and severe hurricanes.

First the Colorado State University tropical forecast team has reduced its prediction for the season from 18 named storms, 9 of which would become hurricanes and 4 severe hurricanes, down to 18 named storms, 8 hurricanes and 3 severe hurricanes.

The CSU team said that they have lowered their forecast slightly due to anomalous cooling of the eastern subtropical and tropical Atlantic that has been observed in recent weeks. Sea level pressure have remained low in June and July and the Pacific maintains cool neutral ENSO conditions, which are prime conditions for tropical formation in the Atlantic, but the anomalous cooling of sea surface temperatures in the Atlantic are typically associated with less favourable conditions for development and hence the reduction in the forecast.

The other forecaster which has updated its figures is Weather Services International (WSI) which has changed its forecast from 16 named storms, 9 hurricanes and 4 severe hurricanes, down to 16 named storms, 8 hurricanes and 3 severe hurricanes.

WSI’s chief meteorologist Dr. Todd Crawford also cited sea surface temperatures when he commented; “North Atlantic temperatures have not warmed as fast as expected this summer, and the most recent runs of our statistical and dynamical models reflect this with lower forecast numbers going forward. The main drivers of tropical activity this year are simply not that remarkable relative to recent years, so a further reduction to the forecast numbers is warranted. There is still a slight chance that a new El Nino event will develop during the next couple of months, which would lower expectations further, but we do not currently see that possibility being much of a factor.”

The reductions in the forecast from these two organisations does not change the average of the forecasts we follow which remains 16 named storms, 9 hurricanes and 4 severe hurricanes. The outlook for the tropical Atlantic is for it to remain calm for the next week, with conditions not conducive to tropical development, but we are now entering the peak of the season and tropical storm formation is likely during the course of August.

As ever, keep in touch with the hurricane season as it develops with our 2013 Atlantic Hurricane Season page.

Update: Tropical Storm Risk has also reduced its forecast, from 15.6 named storms, 7.7 hurricanes and 3.5 major hurricanes, down to 14.8 named storms, 6.9 hurricanes and 3.0 major hurricanes.

This reduction in forecast by another source is still not enough to reduce the average of the forecasts we follow, which remains 16 named storms, 9 hurricanes and 4 severe hurricanes.

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